import time
scale = 50
print("执行开始".center(scale//2,"-"))
start = time.perf_counter()
for i in range(scale+1):
    a = '*'*i
    b = '.'*(scale-i)
    c = (i/scale)*100
    dur = time.perf_counter()-start
    print("\r{:^3.0f}%[{}->{}]{:.2f}s".format(c,a,b,dur),end="")
    time.sleep(0.1)
print("\n"+"执行结束".center(scale//2,'-'))